Artificially constructing mixed bacteria system for bioaugmentation of nitrogen removal from saline wastewater at low temperature

To alleviate the inhibition effects of multi-stresses, a multi-bacterial bioaugmentation based on stimulating cell-to-cell interactions was applied to improve the stress potential of salt-tolerant aerobic granular sludge (AGS). Results showed that the consortium formed by a combination of salt-tolerant ammonia-nitrogen utilizing bacteria, salt-tolerant nitrite-nitrogen utilizing bacteria and salt-tolerant nitrate-nitrogen utilizing bacteria with a whole biomass ratio of 1:2:1 achieved maximum nitrogen consumption rate (μNH4+-N, μNO2--N and μNO3--N of 1.03, 0.57 and 11.62 mgN/L·h, respectively) at 35 gNaCl/L salinity and 15 °C. The flocculent consortium was aggregated by Aspergillus tubingensis mycelium pellet, which was made into a compound bacterial agent (CBA), and the comprehensive nitrogen consumption capability of CBA was further improved to 2.47-4.36-fold of single functional bacteria. 5% CBA (m/m) was introduced into the seafood processing wastewater in batches, in winter (12-16 °C), the removal efficiencies of NH4+-N and total nitrogen increased from 66.89% to 52.77% of native AGS system to 79.02% and 69.97% of nascent bioaugmentation system, respectively. The analysis of key enzyme activities demonstrated that the ammonia monooxygenase and nitrate reductase activities of the bioaugmentation system were increased to 2.73-folds and 1.94-folds those of the native system. Moreover, due to an increase of 6.18 mg/gVSS and 0.11 in the secreted exopolysaccharide and tightly-bound/total extracellular polymeric substances, respectively, bioaugmentation boosted the cell bioflocculation ability by 13.53%, which enhanced the robustness. This work provided a detailed and feasible technical proposal for enhancing the biological treatment performance of saline wastewater in cold regions.